Chloramine vs Chlorine: Which Is in Your City Water (and Why Your Filter Cares)
City Water Disinfection Guide
Chloramine vs Chlorine: Which Is in Your City Water (and Why Your Filter Cares)
Every public water system in America disinfects with one of two chemicals: chlorine or chloramine. They do the same job at the treatment plant, but they behave completely differently in your home, and they do not come out of your water the same way. After 32 years in water treatment, the single most common mistake I see city-water homeowners make is buying a filter built for chlorine when their utility actually uses chloramine. This guide explains the difference in plain language, shows you how to find out which one is in your water, and covers what actually removes each.
The Short Version
- Chlorine is a strong, fast-acting disinfectant that fades as water travels through pipes. It gives water that swimming pool smell, and almost any activated carbon filter removes it easily.
- Chloramine is chlorine bonded to ammonia. It is weaker but far more stable, so it survives long distribution systems. It has less odor, it does not evaporate out of a glass overnight, and standard carbon filters struggle with it. Removing it takes catalytic carbon and adequate contact time.
- Finding out which you have takes five minutes: check your utility's annual water quality report, or run the free-vs-total chlorine comparison covered in our chloramine testing guide.
- If you want it out of every tap, a properly sized catalytic carbon unit is the fix. Browse the options in our whole house water filtration system for city water collection, or start with the dedicated whole house carbon filters lineup.
- Not sure what else is in your water? The City Water Test Kit ($199) checks 47 contaminants at a certified lab, including free chlorine, total chlorine, and chloramine, so you size the right system the first time.
Which Disinfectant Is in Your Water?
Answer two quick questions and I'll point you to the right next step.
Don't buy anything yet. Your utility publishes which disinfectant it uses in its annual water quality report. Our CCR reading guide shows you exactly where to look, and the whole house collection page has a free city water report lookup that pulls the public records for your ZIP code.
Want lab-verified numbers from your own tap, including chloramine? The City Water Test Kit ($199) covers 47 contaminants through a certified lab.
What This Article Covers
- What Chlorine Is (and Why Cities Use It)
- What Chloramine Is
- Why So Many Utilities Switched to Chloramine
- Chloramine vs Chlorine: Side by Side
- How to Find Out Which One Your City Uses
- Why Chloramine Is Harder to Remove
- What Actually Removes Each One (and What Doesn't)
- When You Don't Need to Do Anything
- Frequently Asked Questions
What Chlorine Is (and Why Cities Use It)
Chlorine has been the standard drinking water disinfectant in the United States for over a century, and it deserves the credit it gets. Adding chlorine to public water supplies is one of the biggest public health wins in history: it ended the waterborne typhoid and cholera outbreaks that used to kill people in American cities every year. The CDC still describes chlorination as one of the most important advances in public health.
Chemically, chlorine in water forms what's called free chlorine: a strong, fast-acting oxidizer that kills bacteria and viruses on contact. That strength is also its weakness. Free chlorine is volatile and reactive. It off-gasses out of water (which is why a glass left on the counter smells less chlorinated the next morning), and it burns off as it reacts with organic material in the pipes on the way to your house. A utility with a large distribution system has to add enough chlorine at the plant that there's still a measurable residual at the last house on the line. The people closest to the plant get the strongest dose, and the swimming pool taste that comes with it.
What Chloramine Is
Chloramine is chlorine chemically bonded to ammonia. Utilities create it on purpose by adding ammonia to chlorinated water, a process called chloramination. The form used in drinking water is mostly monochloramine. According to the EPA, more than one in five Americans drinks water disinfected with chloramine, and large cities like Denver and Philadelphia have used it as part of their treatment process for decades. This is not a new or experimental chemical.
The ammonia bond changes everything about how the disinfectant behaves:
- It's more stable. Chloramine doesn't burn off or evaporate the way free chlorine does. It holds its disinfecting power all the way through miles of water mains, which is exactly why big cities like it.
- It's milder to the senses. Chloraminated water usually has less of the sharp pool smell. Plenty of homeowners on chloraminated water assume their water has "no chlorine in it" because they can't smell it.
- It's a weaker disinfectant, used for a different job. Most systems that use chloramine still disinfect with something stronger at the plant, then convert to chloramine as the long-lasting residual for the trip through the pipes.
- It's much harder to get rid of. The same stability that helps the utility works against you at home. It won't off-gas out of a pitcher overnight, boiling takes far longer than is practical, and standard carbon filters bleed it through. More on that below.
Why So Many Utilities Switched to Chloramine
The switch wasn't about cost or convenience. It was about regulations on disinfection byproducts.
When free chlorine reacts with natural organic matter in source water (decaying leaves, algae, sediment), it creates byproducts called trihalomethanes (TTHMs) and haloacetic acids (HAA5). Long-term exposure to these byproducts is associated with health risks, so the EPA capped them: 80 parts per billion for TTHMs and 60 parts per billion for HAA5 under the Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules.
Here's the bind utilities found themselves in: they must keep a disinfectant residual in the pipes (that's non-negotiable for preventing bacterial regrowth), but the more chlorine they add, the more byproducts they create. Chloramine offered a way out. Because it's less reactive, it produces far lower levels of the regulated byproducts while still maintaining a residual to the end of the line. For a utility trying to stay under the EPA caps with challenging source water, switching the residual to chloramine is often the most practical compliance path.
The trade-offs are real, though, and worth stating plainly:
The honest fine print on chloramine
Lead leaching: Changing water chemistry can destabilize the mineral scale that coats the inside of old lead pipes. Washington, DC learned this the hard way after switching to chloramine in the early 2000s, when lead levels in some homes spiked. Utilities now manage this with corrosion inhibitors, but if your home predates 1986 and might have lead plumbing, that's worth testing regardless of which disinfectant your city uses.
Dialysis and aquariums: Both chlorine and chloramine must be completely removed from water used for kidney dialysis and fish tanks. Chloramine is the bigger trap because people don't realize it's there and it doesn't gas off if you let the water sit.
Rubber and gaskets: Chloramine is harder on certain rubber plumbing components (toilet flappers, faucet washers, some supply line gaskets) than chlorine is. If you're on chloraminated water and your flappers keep degrading, that's not your imagination.
None of this makes chloraminated water unsafe at regulated levels. Both disinfectants are federally capped at a residual of 4 milligrams per liter, a level the EPA considers safe for drinking. If you want the deeper health discussion, I wrote a separate piece on that: Is Chlorine in Water Bad for You?
Chloramine vs Chlorine: Side by Side
Fast, strong, short-lived
- Strong oxidizer, kills pathogens quickly
- Noticeable pool smell and taste
- Dissipates from a glass in about a day
- Boils off quickly
- Any quality carbon filter removes it
Milder, stable, persistent
- Weaker oxidizer, but lasts for miles of pipe
- Little to no smell in most homes
- Persists in standing water for days
- Resists boiling and off-gassing
- Needs catalytic carbon plus contact time
| Chlorine (free chlorine) | Chloramine (monochloramine) | |
|---|---|---|
| What it is | Chlorine dissolved in water | Chlorine bonded to ammonia |
| Disinfecting strength | Strong, fast-acting | Weaker, slow and steady |
| Stability in pipes | Fades over distance | Stays effective to the end of the line |
| Taste and odor | Distinct pool smell, especially near the plant | Milder; many people can't smell it at all |
| Regulated byproducts (TTHMs/HAA5) | Higher formation | Much lower formation of regulated DBPs |
| EPA residual limit | 4 mg/L | 4 mg/L |
| Evaporates if water sits out | Yes, roughly a day | No, persists for days |
| Removed by standard activated carbon | Yes, easily | Poorly; bleeds through undersized filters |
| Removed by catalytic carbon | Yes | Yes, with adequate contact time |
| Dialysis / aquarium concern | Yes, must be removed | Yes, and it's the one that catches people off guard |
How to Find Out Which One Your City Uses
You have three ways to answer this, from easiest to most thorough.
1. Read your utility's annual water quality report
Every community water system publishes a Consumer Confidence Report (CCR) each year. Look for the disinfectant listed in the detected contaminants table: it will say "chlorine" or "chloramines" (sometimes "total chlorine" with a note about chloramination). My guide to reading your water quality report walks through the whole document line by line. If you'd rather not dig for the PDF, the free city water report lookup on our whole house filtration collection page pulls the public records for your ZIP code in a few seconds.
2. Call your utility
The phone number is on your water bill. Ask: "Do you disinfect with free chlorine or chloramine?" The operator on duty answers this question all the time, and some systems switch seasonally (free chlorine flush in spring, chloramine the rest of the year), which the CCR doesn't always make obvious.
3. Test it yourself: the free vs total chlorine trick
A simple two-part test at your tap settles it. Free chlorine and total chlorine test strips (or a pool-style DPD test) measure different things, and the gap between them is chloramine. If total chlorine is high but free chlorine is near zero, you're on chloramine. I cover the exact procedure, what strips to buy, and how to read the results in the dedicated guides: how to test for chloramine and how to test for chlorine.
If you're already planning treatment, skip the strips and get lab numbers for everything at once. The City Water Test Kit ($199) reports 47 contaminants from a certified lab, including free chlorine, total chlorine, chloramine, lead, and the disinfection byproducts. Test first, buy second. That order matters, because the test result decides which media and which size actually solve your problem.
Why Chloramine Is Harder to Remove
This is the part that costs homeowners money when they get it wrong, so let me explain the mechanism instead of just asserting it.
Standard activated carbon removes free chlorine almost instantly. The carbon surface chemically reduces chlorine on contact, which is why even a cheap fridge filter takes the pool taste out. Chloramine is a different problem for two reasons:
- The ammonia bond resists the reaction. Breaking chloramine apart on a carbon surface is a slower catalytic reaction, not the quick reduction that kills free chlorine. Standard carbon does it, but slowly and inefficiently, and its capacity for chloramine exhausts far faster than its chlorine capacity.
- Contact time becomes the limiting factor. Because the reaction is slow, the water has to spend enough time in the media bed. A small cartridge at full household flow gives chloramine a fraction of a second of contact. It bleeds straight through. This is why people install a 10-inch cartridge "whole house chlorine filter," still smell nothing (chloramine never smelled), and then wonder why their skin is still irritated and their fish still die.
The fix is catalytic carbon: activated carbon whose surface has been modified at the factory to speed up exactly this reaction. It removes chloramine several times more efficiently than standard carbon, and it handles free chlorine just as well. The catalytic grade we use is Centaur, made by Calgon Carbon, the same catalytic media municipal treatment plants themselves buy when they need to remove chloramine. I wrote a full comparison of the two media types here: Catalytic Carbon vs Standard Activated Carbon.
Even with catalytic carbon, size still matters. A bigger media bed means more contact time at the same flow rate. That's why my chloramine recommendations lean toward the 2.5 cubic foot tank for average homes rather than the smallest unit that technically fits the plumbing.
What Actually Removes Each One (and What Doesn't)
To be clear about intent: this is not a buyer's guide, and I'm not ranking products here. If you're ready to compare specific whole house systems, that's covered in Best Whole House Water Filter for Chlorine. What follows is the honest map of which removal methods work on which disinfectant.
Whole house catalytic carbon
A tank of catalytic carbon at the point of entry treats every tap: showers, laundry, ice maker, everything. For most 2 to 4 bathroom homes I spec the Clack 2.5 cubic foot non-backwashing carbon filter ($1,695) with Centaur catalytic carbon. No drain, no electricity, no moving parts: water simply flows through the media bed and the disinfectant is caught and broken down in the tank. Smaller homes (1 to 2 bathrooms) can run the 1.5 cubic foot version ($1,495). If your water also carries sediment, a backwashing carbon filter rinses its own bed on a schedule; the whole house carbon filter collection has both styles.
On chlorine-only water, standard carbon also works fine at this scale. I default to catalytic anyway: it costs little more, and if your utility converts to chloramine later (the regulatory pressure only points one direction), your filter already handles it.
Under-sink reverse osmosis
An RO system's carbon pre-filters remove the disinfectant and its byproducts before the membrane polishes off nearly everything else. For drinking and cooking water this is the most complete option, and at $275 for the MAW-50 it's the budget-friendly one too. The limitation is scope: it treats one faucet. It does nothing for showers, laundry, or skin exposure. On chloraminated water, keep up with the pre-filter changes; exhausted carbon lets chloramine reach the membrane, and chloramine shortens membrane life.
Standard carbon cartridges, pitchers, and fridge filters
For free chlorine taste and odor at low flow, these are honestly fine. For chloramine they are not. Capacity exhausts quickly and contact time is too short at anything above a trickle. If a pitcher is what your budget allows and your city uses chloramine, look specifically for cartridges rated for chloramine reduction under NSF/ANSI 42, expect short cartridge life, and treat it as a drinking-water-only measure.
Vitamin C (ascorbic acid)
Ascorbic acid neutralizes both chlorine and chloramine on contact. It's the standard method for dechlorinating bath water for sensitive skin and for aquarium water conditioning. It's a fix for a bucket or a bathtub, not a house.
Letting water sit, boiling, water softeners, sediment filters
Letting a pitcher sit overnight works for chlorine and does nearly nothing for chloramine; it can hang on for days. Boiling drives chlorine off in minutes but takes impractically long for chloramine. Water softeners exchange hardness minerals and do not remove either disinfectant (in fact, chlorine and chloramine slowly degrade softener resin, which is why a carbon tank goes upstream of a softener on city water). Sediment filters catch particles, not dissolved chemicals.
What this looks like on real phone calls
Most of what I know about how homeowners experience this comes from the phone. A Los Angeles city employee called this spring about hard water at his house; when I asked whether he was on city or well water, the answer settled the whole design: city water means the carbon tank goes first, then the softener, because the carbon protects the softener resin from the disinfectant. Another caller on a chlorinated community well asked why I kept recommending the tank-style unit over the cartridge housing he'd seen online. The answer is the same one in this article: contact time. As I tell customers, the non-backwashing carbon tank "doesn't have to backwash, it doesn't need electricity. Water just flows through, and chlorine and chlorine byproducts are absorbed and held in the tank."
"Great Product Great Support. I did this myself with Iron Filter, water softener, and carbon tank. Great support from Aiden. Be careful with the outflow connections I had to use tape and dope to stop drip and backwash lines air gap need to be to code."
When You Don't Need to Do Anything
It's fine to leave your water alone
Both disinfectants are doing a legitimate job: keeping the water safe between the plant and your faucet. If your water tastes fine to you, your skin isn't irritated, nobody in the house is on home dialysis, you don't keep fish, and your test results are clean, you don't need a filter. I'd rather tell you that now than sell you a tank you didn't need.
The people who genuinely benefit from removing chlorine or chloramine at home are the ones who notice the difference: taste and odor complaints, dry or irritated skin and eczema flare-ups that improve on vacation, aquarium keepers, home dialysis patients (talk to your care team; this is their protocol, not mine), homebrewers and sourdough bakers (chloramine interferes with yeast and produces off-flavors), and anyone whose test shows elevated disinfection byproducts alongside the residual. If that's you, the fix is well understood and sized in an afternoon phone call.
For the bigger picture of treating municipal water (sediment, hardness, lead, PFAS, and where disinfectant removal fits among them), start with the City Water Treatment Guide, or go deeper on the media itself in the complete guide to carbon filters.
Frequently Asked Questions
How do I tell if my water has chlorine or chloramine?
Check your utility's annual water quality report (CCR), which names the disinfectant, or call the number on your water bill and ask. To confirm at your own tap, test free chlorine and total chlorine separately: if total is high but free is near zero, you have chloramine. Our chloramine testing guide covers the exact procedure.
Is chloramine more toxic than chlorine?
No. At the levels allowed in drinking water (both are capped at a 4 mg/L residual by the EPA), neither is considered a health risk for the general population. The meaningful differences are practical: chloramine is harder to remove, it must be filtered out for dialysis and aquariums, and it forms fewer of the regulated disinfection byproducts than chlorine does. Water chemistry changes during a chloramine conversion can temporarily increase lead leaching in homes with lead plumbing, which utilities manage with corrosion inhibitors.
Does boiling water remove chloramine?
Not practically. Boiling drives off free chlorine within a few minutes, but chloramine's ammonia bond resists off-gassing, so removing it by boiling takes far longer than anyone realistically boils water. Letting water sit out overnight has the same problem: chlorine dissipates in about a day, chloramine persists for days. Catalytic carbon filtration or ascorbic acid (vitamin C) are the practical removal methods.
Does a regular carbon filter remove chloramine?
Only partially, and it exhausts quickly. Standard activated carbon removes free chlorine easily but reacts with chloramine slowly, so at normal household flow rates chloramine bleeds through small cartridges and pitcher filters. Effective chloramine removal takes catalytic carbon (a surface-modified activated carbon) and enough media volume to provide contact time. See catalytic vs standard carbon for the full comparison.
Do pools use chlorine or chloramine?
Pools use free chlorine as the sanitizer. The chloramines in pools are actually the unwanted byproduct: they form when chlorine reacts with sweat and other nitrogen compounds from swimmers. That sharp "pool smell" and eye sting is mostly chloramines, which is why pool operators "shock" the water with extra chlorine to break them down. Drinking water chloramination is different: utilities intentionally form stable monochloramine as a long-lasting disinfectant.
Is chloramine safe for fish and aquariums?
No. Both chlorine and chloramine are toxic to fish, and chloramine is the one that catches aquarium keepers off guard because it does not evaporate if you let tap water sit out overnight, the way chlorine does. Use a water conditioner rated for chloramine (most modern ones neutralize both and detoxify the released ammonia), or fill from a tap fed by a reverse osmosis system or catalytic carbon filter.
Why does my tap water smell like a swimming pool?
A strong chlorine smell usually means your home is relatively close to the treatment plant or a booster station, where the free chlorine residual is highest, or your utility is running its annual free-chlorine flush. The smell itself is a nuisance rather than a danger at regulated levels. Any quality activated carbon filter will remove it; a whole house carbon system takes it out of showers too, where hot water releases the most odor. If the smell appeared suddenly and is paired with discoloration, call your utility first.
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About the Author: Aidan has been in the water treatment industry for 32 years, including 28 years of hands-on installations and service. Mid Atlantic Water is a wholesale distributor that ships commercial-grade water treatment systems directly to homeowners, cutting out the dealer markup and commissioned salespeople. Every recommendation in this article is based on field results from thousands of installations, not theory or affiliate commissions.
Not sure whether your city uses chlorine or chloramine? Call or text Aidan at 800-460-5810 · Email support@midatlanticwater.net